The study of differential mortality rates from leading causes of death by ethnic group may provide insights to understanding the role of cultural and environmental factors in the causation of disease. A major obstacle to studying ethnic differentials in mortality on a national or sub-national basis in recent years has been the lack of information on country of birth or ancestry in tabulated mortality data. An alternative approach, suggested by a number of studies of socioeconomic variation in mortality, is the utilization of existing death record data for metropolitan places coded according to census tract of residence. The proposed study involves using census tract data, as coded by state and local health departments, to estimate mortality rates from leading causes among selected ethnic groups for the period around 1980. Deaths for the three years 1979-1981 among residents of seven of the largest U. S. cities or metropolitan countries will be obtained and related to 1980 census populations to compute age-adjusted mortality rates, by sex, for major causes. Within age-sex categories, the number of deaths in each tract will be regressed on the tract population of each ethnic group. The coefficients would then represent estimates of age- and sex-specific death rates for each ethnic group. An attempt will also be made to estimate mortality rates directly in heavily ethnic areas. Data for individual places wil be looked at separately and in combination with others. Data will be produced for six ethnic groups.